ST-506
The ST-506 was the first 5.25 inch hard disk drive, introduced in 1980 by Seagate Technology (then Shugart Technology) It stored up to 5 megabytes after formatting and cost $1500. The similar (but more expensive) 10 MB ST-412 was introduced in late 1981. Both used MFM encoding, a widely used coding scheme. A subsequent extension of the ST-412 used RLL for a 50% boost in capacity and bit rate.
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